LowReynoldsnumber

The Reynolds number is a dimensionless quantity used in fluid mechanics to predict flow patterns in different fluid flow situations. It is a ratio of inertial forces to viscous forces. A low Reynolds number signifies that viscous forces are dominant over inertial forces. This typically occurs when a fluid is moving very slowly, or when the fluid is very viscous, or when the characteristic length scale of the flow is very small.

In the regime of low Reynolds numbers, often referred to as laminar flow, the fluid moves in smooth layers, with no disruption or intermixing between these layers. This is in stark contrast to high Reynolds number flows, where inertial forces dominate, leading to chaotic and turbulent motion. Examples of low Reynolds number flows are common in microscopic environments. For instance, the movement of microorganisms like bacteria in water, or the flow of blood in tiny capillaries, often occurs at low Reynolds numbers. Similarly, the lubrication of surfaces by thin films of oil, or the flow of molten glass, can also be characterized by low Reynolds numbers.

The mathematical definition of the Reynolds number (Re) is given by Re = (ρ * v * L) / μ, where ρ is the fluid density, v is the flow velocity, L is a characteristic linear dimension, and μ is the dynamic viscosity of the fluid. When Re is significantly less than 1, the viscous forces essentially dictate the fluid's behavior. This dominance of viscosity leads to a predictable and orderly flow.